A new loricariid catfish is described from the Tremembé Formation (Late Oligocene to Early Miocene) sediments of the Taubaté Basin in eastern São Paulo State, Brazil. Taubateia paraiba, new genus and species, is based on a single specimen preserved as a ventral-side impression of an articulated partial neurocranium, dorsal elements of the pectoral girdle and anterior vertebrae. The fossil is identified as belonging to family Loricariidae based on obvious overall similarity and the presence of diagnostic derived characters such as: odontodes, dorsal margin of metapterygoid contacting lateral ethmoid, presence of mesethmoid disk (condyle), and compound pterotic-supracleithrum bone. Also, as in most loricariids, the ossified transcapular (Baudelot's) ligament plus basiocciptal lateral process form a prominent transverse wall at the occiput. Other derived characters preserved in Taubateia are synapomorphies at different levels within Loricariidae, including a wide and low parasphenoid, form of pterotic-supracleithrum, shape and position of the mesethmoid disk, a triangular lateral ethmoid with expanded posterolateral corner and a rounded and low ridge articulating with the metapterygoid, and a pointed distal margin of transverse process of the Weberian compound centrum. The derived characters recognized in this fossil are a distinctive combination for diagnosing a new genus and species but not for its unambiguous placements in any of the currently recognized loricariid subfamilies.

The Taubaté rift basin in eastern São Paulo State, Brazil, is drained by the modern Paraíba do Sul River (Fig. 1). This structural basin and three others in eastern Brazil form the continental rift of southeastern Brazil (CRSB), which is associated with continental break-up and the continuous opening of the Atlantic Ocean. During the Eocene-Oligocene took place the main development phase of the CRSB with the formation of a continuous central hemigraben: São Paulo, Taubaté, Resende, and Volta Redonda. The sedimentation of this phase is represented by the Taubaté Group including the Resende (basal), Tremembé (middle) and São Paulo (top) formations (Riccomini et al., 1987, 2004; Riccomini, 1989). The Tremembé Formation is a lacustrine sedimentary unit in the Taubaté basin dated as Late Oligocene to Early Miocene (~30-20 Myr) based on its fossil content (Lima et al., 1985; Lundberg et al., 1998; Soria & Alvarenga, 1989).

Remains of siluriforms are common in the Taubaté Basin and include articulated skeletons and detached elements belonging to the pimelodid Steindachneridion. These fossils occur in two levels of the Tremembé Formation: montmorilonite clays and dark greenish shales. Two fossil species of Steindachneridion were described from the Tremembé Formation: S. iheringi (Woodward, 1898) and S. silvasantosi Figueiredo & Carvalho (1999a).

Despite the recent diversity, fossil loricariid records are extremely rare. Malabarba (1988) reported isolated body plate and fin spines of a yet indeterminate loricariid catfish from the Tremembé Formation. More recently, loricariid remains have been identified in the Miocene sediments of the La Venta Group in Colombia (Lundberg, 1997) and Puerto Madryn Formation of the Argentinian Patagonia (Cione et al., 2005). In this paper we describe and illustrate a single loricariid specimen represented by an articulated ventral side impression of the neurocranium and most anterior vertebrae. Although the information is limited, the characters recognized are sufficient to diagnose the fossil as a new genus and species.

Material and Methods

The specimen described herein (DGM 17-P) comes from the sediments of Tremembé Formation, Taubaté Tertiary Basin, eastern São Paulo (Fig. 1). It is deposited in the collection of the Museu de Ciências da Terra of the Departamento Nacional de Produção Mineral (DNPM), Rio de Janeiro, Brazil. This specimen was listed among the examined materials in the redescription and reconstruction of Steindachneridion iheringi (Figueiredo & Carvalho, 1999b:871, 873).

The general anatomical terminology used here follows Schaefer (1997) with the compound pterotic-posttemporal-supracleithrum bone being referred to simply as pterotic. Comparisons to modern fishes were made with cleared and stained (C&S) or dry skeletons (skel) as noted below.

Description. The description is necessarily limited to the ventral view of the head skeleton and anterior vertebrae.

Neurocranium. The neurocranium is roughly triangular in outline shape, narrow anteriorly and greatly expanded across the occipital region. The arrangement and shapes of cranial bones resemble those of other loricariids, and show typical loricariid features, such as: vertical projection in the anterior end of mesethmoid; the reduced mesethmoid cornua, triangular shaped and expanded lateral ethmoids, a compound pterotic posteriorly expanded.

The mesethmoid is a triangular bone, anteriorly narrow and pointed, and expanded posteriorly. It is flattened with lateral expansions (crest of Py-Daniel, 1997) incorporated into the main body of the bone, as occurs in the depressed species. It presents the typical pair of greatly reduced and rounded anterolateral cornua, each with a shallow concavity in the center and a few grooves in the cornua base. The anterior edge of the mesethmoid is smooth with a small median cleft between the cornua. A moderately developed rounded disk (condyle) projects ventrally from the mesethmoid behind the cornua; there are no signs of concave facets on the disk but two depressions are present laterally. Based on the good preservation of this specimen, particularly the mesethmoid region, we may assume that these facets did not exist. The mesethmoid disk has a subterminal position, not contacting the anterior margin of the mesethmoid and would not be visible in a dorsal view. Posteriorly, the mesethmoid meets the prevomer in a V-shaped suture.

The prevomer has the shape of an elongated diamond with small lateral wings contacting the mesethmoid and the lateral ethmoid. The anterior end is moderately developed as a pointed spike that deeply interdigitates with the mesethmoid. Its posterior end is an elongate spine that extends between a pair of parasphenoid spikes.

The paired lateral ethmoids are large and triangular with the posterolateral corner expanded. The lateral ethmoid anterior border is straight and bears an anterolateral articular facet for the palatine. The lateral ethmoid expands posteriorly to form a distinct lateroposterior process at the anterior margin of the orbit. A low ridge, rounded in cross-section, extends longitudinally near the lateral ethmoid margin from the palatine articular facet to the posterior border to terminate at an ovoid condyle that would presumably articulate with dorsal surface of the metapterygoid. According to Py-Daniel (1997:38), regardless of the extent of contact between lateral ethmoid and metapterygoid, the posterior end of the lateral ethmoid is always involved via a condyle or suture. The state of preservation does not allow us to determine the structure of the nasal capsules.

The parasphenoid lies flat on the ventral midline between the prevomer anteriorly to basioccipital posteriorly. Anteriorly the parasphenoid forms a wide and slightly raised ridge separating the lateral ethmoids; posteriorly its margin is gently curved laterally below the orbitosphenoid, and expanded, forming small lateral wings in contact with the prootics. The posterior margin of the parasphenoid strongly interdigitates with the basioccipital across the ventral midline.

The basioccipital is laterally sutured with the prootic and exoccipital. Its lateral process contacting with the mesial end of the ossified transcapular (Baudelot's) ligament of the posttemporal-supracleitrum that continues laterally forming a wall sutured to the exoccipital and pterotic. In a developmental study of the skeleton of the loricariid Ancistrus cf. triradiatus, Geerinckx et al. (2007) show that the ossification of the transcapular ligament arises from two sources: medially from the basioccipital (our "basioccipital lateral process") and laterally from the pterotic-supracleithrum (our ossified transcapular ligament).

The orbitosphenoid is nearly retangular in form with concave lateral margins. It is sutured to the lateral ethmoid anteriorly, and with the prootic posteriorly. Despite the large expansion of the lateral ethmoid posterior border, the orbitosphenoid does not follow this enlargement, and the anterior (with the lateral ethmoid) and the posterior (with prootic) sutures remain with similar lengths.

The exoccipitals are a small pair of bones limited anteriorly by the prootic and mesially by the basioccipital. Posteriorly, the exoccipital remains limited by the basioccipital lateral process and transcapular ligament. The exoccipital is pierced by the two foramina for the glossopharyngeal and vagus nerves, near its posterior border.

The prootic forms the ventrolateral floor of the neurocranium posterior to the orbitosphenoid. It is a large bone sutured posteriorly to the basioccipital, exoccipital and pterotic. A circular notch is present in the anterolateral border of the prootic representing the trigeminofacial foramen. Almost in the center of the bone there is a smaller foramen presumably for the hyomandibular branch of the facial nerve.

Generally in loricariids the sphenotic is a paired bone mostly developed and visible on the dorsal side of neurocranium. However, in DGM 17-P a portion of this bone is preserved in a ventral view, displaying its anterior suture to the frontal and the spine projected from its lateral border. Some odontode marks can be observed along the sutures and lateral border of the sphenotic. Even a few odontodes are preserved scattered in the sediment.

The paired pterotics are broad compound bones (pterotic + supracleithrum) forming most of the posterolateral part of the skull. Each pterotic is greatly expanded and squarish in shape with the lateral margin nearly straight. The ventral surface of the pterotic bears a strong ridge for pectoral girdle articulation. Posteriorly it is closely associated but not fused with the transverse processes of complex vertebrae. The ventral aspect of Taubateia shows the transverse process of the Weberian compound centrum surrounding the swimbladder.

Weberian apparatus and anterior axial skeleton. The Weberian complex centrum is almost square and relatively short, not much longer than the seventh centrum. It is fused to the basioccipital anteriorly and sutured to the sixth vertebrae centrum posteriorly. The transverse process and the complex centrum form nearly a 70º angle, being slightly ventrally directed. The distal tip of the transverse process of the Weberian complex centrum is in contact with the pterotic with about the same width than the shaft. It is distally rounded (not pointed) and cancellous.

In addition to the vertebrae incorporated into the Weberian apparatus, vertebral centra six through nine are preserved. The sixth centrum has a large pair of ventrolaterally placed facets for articulation with the first pair of ribs. The aortic groove runs open and delimited by laminar bone from the complex centrum to at least the vertebra centrum 9.

Etymology. The specific name paraiba (a noun in apposition) refers to the modern river Paraíba do Sul, which crosses the geological basin where the fossil was collected; gender feminine.

Discussion

The fossil specimen described herein is the sole representative of its taxon and preserves only a ventral side impression of the neurocranium and anterior vertebrae. Consequently, the observable features for this species are limited to a small fraction of those documented in broader comparative and phylogenetic studies of Loricariidae (e.g. Schaefer, 1987, 1991, 2003; Py-Daniel, 1997; Armbruster, 2004). Nevertheless, some of the preserved characters are derived states and recognized as synapomorphies for monophyletic subgroups within Loricariidae.

Despite of the limited information, Taubateia can be phylogenetically placed in family Loricariidae based on the presence of three synapomorphies: dorsal margin of the metapterygoid contacting the lateral ethmoid (Schaefer, 1987; Armbruster, 2004: character 97), which can be inferred from the presence of the lateral ethmoid ridge and condyle; a mesethmoid disk (Armbruster, 2004: character 100); pterotic fused with supracleithrum and expanded posteriorly (Schaeffer, 1987). In addition, Taubateia shows an ossified transcapular (Baudelot's) ligament forming a distinct wall along the occiput, as occurs in most loricariids (Neoplecostominae, Hypoptopomatinae, Loricariinae and Hypostominae; Armbruster, 2004: character 93).

Some derived characters associated with loricariid subfamilies or genera are preserved in T. paraiba. Thus, we recognize characters of the Loricariinae: a wide and low parasphenoid, the shape of pterotic, and the size and position of the mesethmoid disk. Although, none of the foregoing are among the unambiguous changes listed for Loricariinae by Armbruster (2004) Taubateia shares the following derived character with subgroups within Loricariinae: a trapezoidal pterotic widest ventrally (108:1) is shared with the Loricariini (Loricariichthys, Loricaria, Crossoloricaria, Rineloricaria, Ixinandria in Armbruster's analysis); a wide and only slightly raised parasphenoid (character 106, state 1) is shared with Loricarichthys, Loricaria and Crossoloricaria (clade 28); and a longitudinal, low ridge on lateral ethmoid shared with Harttia and Lamontichthys.

Of the 29 synapomorphies listed by Py-Daniel (1997) for Loricariini, two are preserved in T. paraiba: parapophyses of the fourth vertebrae (transverse process of Weberian complex centrum) reaching the border of the pterotic; and contact of the lateral ethmoid with the suspensorium via broad suture (this is assumed from the presence of a lateral ethmoid ridge). Among these loricariin synapomorphies is the basioccipital not sutured to ossified transcapular (Baudelot's) ligament; with the exoccipital between the two bones (character 18, state 1). In Taubateia, the basioccipital is in contact with the ligament and the exoccipital lies at the corner formed by them (character 18, state 0) as occurs in Hemiodontichthys (a reversion) in this tribe.

However, derived characters of T. paraiba shared with subfamilies other than Loricariinae, create a conflicting pattern precluding a clear assignment of the fossil to a subfamily. Among these are a triangular lateral ethmoid with a longitudinal ridge and a posterior condyle (or facet) for contacting the metapterygoid. The triangular lateral ethmoid with greatly expanded posteroventral corner of Taubateia is synapomorphic for some hypoptopomatines (Armbruster, 2004: character 95, state 1). The presence of the ridge is widespread in loricariids, but it is rounded and low (character 97, state 1) in Hypostominae, some loricariines (Harttia sp, Lamontichthys), most hypoptopomatines (Armbruster, 2004: clade 16), and is also present in Lithogenes. On other hand, an additional posterior condyle for articulating with metapterygoid is synapomorphic for Hypostominae plus Ancistrinae (Schaefer, 1987). Still, Taubateia shares a wide and flat parasphenoid with Rhinelepini (in special with Pseudorinelepis) and the absence of ribs posterior to the sixth vertebra (Armbruster, 1998).

In the redescription of Lithogenes villosus, Schaefer (2003) lists 11 synapomorphies supporting the clade Lithogenes + Loricariidae. Two of these are visible in Taubateia: the presence of a mesethmoid condyle (character 1) and metapterygoid contacting the lateral ethmoid (character 12). The other nine synapomorphies were not preserved and can not be verified in the fossil. Lithogenes is diagnosed by nine synapomorphies, none of which are preserved in Taubateia. The Loricariidae clade, represented in the Schaefer's paper by Loricariichthys, Hemipsilichthys, Neoplecostomus, Parotocinclus, Ancistrus and Kronichthys, is supported by 8 synapomorphies. The character 2, mesethmoid condyle shape, is the only one verifiable in the fossil. Shaefer (2003) defined two states for this character: state 0, spherical as in Lithogenes; and state 1, laterally compressed, discoid as in the Loricariidae clade. In Taubateia the mesethmoid condyle is not discoid; it is round, ball-like, but in a very different way from Lithogenes spherical condyle. Whereas in Lithogenes villosus the condyle is wide, slightly anteriorly projected, with two anterior processes (in Schaefer, 2003: fig. 5), in Taubateia it is small, straight ventrally projected with no processes.

In order to obtain additional information about its phylogenetic relationships, Taubateia was included in the taxon/character matrix of Schaefer (2003) and an exhaustive search using PAUP 3.1 (Swofford, 1993) was performed. This search resulted in 15 most parsimonious trees with length=65, CI=0.754, and RI=0.714. The addition of Taubateia resulted in more numerous trees which are shorter than those obtained by Schaefer (2003, five equally parsimoniuous trees with 66 steps. In the 15 parsimonious trees, three different positions are suggested for Taubateia: as sister group to loricariids (including Lithogenes); as sister group to nonlithogenine loricariids; and as sister-group to Lithogenes and that pair forming the sister group to nonlithogenine loricariids. Other tree topologies vary only in terms of the relative position of the six nonlithogenine loricariid representatives, as occurred in the Schaefer's (2003) analysis. In all trees Taubateia plus Lithogenes plus Loricariids form a monophyletic group. The strict consensus of the 15 equally parsimonious trees shows a polytomy with Taubateia, Lithogenes and loricariids.

Summarizing all above information, Taubateia shows few derived characters which can be considered derived at different levels within loricarioids: mesethmoid slightly cleft with very reduced and rounded lateral cornua; presence of a mesethmoid condyle; mesethmoid condyle, small, spherical and subterminal; mesethmoid shaft wide; posterolateral corner of the lateral ethmoid expanded; lateral ethmoid with rounded ridge for contacting the metapterigoid; parasphnoid on orbitosphenoid wide and flat; transcapular (Baudelot's) ligament forming a wall; relatively short Weberian complex centrum; parapophyses of 4th vertebrae with approximately same length as the pterotic; aortic-groove extending to vertebrae 9; pleural ribs posterior to sixth vertebrae absent; pterotic trapezoidal and expanded posteriorly. At this time the position of Taubateia is uncertain within Loricariidae, the character combination of the fossil does not fit in any of the subfamily diagnoses and this is only partly a result of non-preservation. For this reason, it would be premature to assign the fossil taxon to any subfamily.

Acknowledgements

The authors thank to D. A. Campos and Rita C. Cassab at DNPM-RJ for the loan of fossil specimens for study; and to Kyle Luckenbill for preparing the photo of the modern Hypostomus skull. Thanks also to E. Pereira, P. Lehmann and M. Rodriguez for providing comparative material and information. The U.S. National Science Foundation supported this work through research grant DEB 0089612 to JGL, partial support of publication costs was provided by the All Catfish Species Inventory (NSF DEB 0315963).